DERIVATIVES AND HEDGING - Schedule of Location and Fair Value of Derivative Assets and Liabilities (Details) - USD ($) $ in Millions	Mar. 31, 2026	Dec. 31, 2025
Derivative [Line Items]
Total Assets	$ 1,408	$ 1,357
Total Liabilities	1,180	970
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	228	387
Current Risk Management Assets
Derivative [Line Items]
Total Assets	862	776
Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	546	581
Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	729	532
Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	451	438
AEP TEXAS INC.
Derivative [Line Items]
Total Assets	1	0
Total Liabilities	0	0
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	1	0
AEP TEXAS INC. | Current Risk Management Assets
Derivative [Line Items]
Total Assets	1	0
AEP TEXAS INC. | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
AEP TEXAS INC. | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
AEP TEXAS INC. | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
APCo
Derivative [Line Items]
Total Assets	26	84
Total Liabilities	10	6
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	16	78
APCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	24	82
APCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	2	2
APCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	9	5
APCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	1	1
I&M
Derivative [Line Items]
Total Assets	18	24
Total Liabilities	20	14
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	(2)	10
I&M | Current Risk Management Assets
Derivative [Line Items]
Total Assets	18	23
I&M | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	1
I&M | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	20	13
I&M | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	1
OPCo
Derivative [Line Items]
Total Assets	1	0
Total Liabilities	32	33
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	(31)	(33)
OPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	1	0
OPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
OPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	4	5
OPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	28	28
PSO
Derivative [Line Items]
Total Assets	22	44
Total Liabilities	35	30
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	(13)	14
PSO | Current Risk Management Assets
Derivative [Line Items]
Total Assets	22	44
PSO | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
PSO | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	30	29
PSO | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	5	1
SWEPCo
Derivative [Line Items]
Total Assets	17	37
Total Liabilities	14	13
Total MTM Derivative Contract Net Assets (Liabilities) Recognized	3	24
SWEPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	17	37
SWEPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
SWEPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	11	11
SWEPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	3	2
Commodity | Not Designated as Hedging Instrument | Current Risk Management Assets
Derivative [Line Items]
Total Assets	798	720
Commodity | Not Designated as Hedging Instrument | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	495	518
Commodity | Not Designated as Hedging Instrument | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	693	500
Commodity | Not Designated as Hedging Instrument | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	419	420
Commodity | Not Designated as Hedging Instrument | AEP TEXAS INC. | Current Risk Management Assets
Derivative [Line Items]
Total Assets	1	0
Commodity | Not Designated as Hedging Instrument | AEP TEXAS INC. | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Not Designated as Hedging Instrument | AEP TEXAS INC. | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Not Designated as Hedging Instrument | AEP TEXAS INC. | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Not Designated as Hedging Instrument | APCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	24	82
Commodity | Not Designated as Hedging Instrument | APCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	2	2
Commodity | Not Designated as Hedging Instrument | APCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	9	5
Commodity | Not Designated as Hedging Instrument | APCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	1	1
Commodity | Not Designated as Hedging Instrument | I&M | Current Risk Management Assets
Derivative [Line Items]
Total Assets	18	23
Commodity | Not Designated as Hedging Instrument | I&M | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	1
Commodity | Not Designated as Hedging Instrument | I&M | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	20	13
Commodity | Not Designated as Hedging Instrument | I&M | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	1
Commodity | Not Designated as Hedging Instrument | OPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	1	0
Commodity | Not Designated as Hedging Instrument | OPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Not Designated as Hedging Instrument | OPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	4	5
Commodity | Not Designated as Hedging Instrument | OPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	28	28
Commodity | Not Designated as Hedging Instrument | PSO | Current Risk Management Assets
Derivative [Line Items]
Total Assets	22	44
Commodity | Not Designated as Hedging Instrument | PSO | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Not Designated as Hedging Instrument | PSO | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	30	29
Commodity | Not Designated as Hedging Instrument | PSO | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	5	1
Commodity | Not Designated as Hedging Instrument | SWEPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	17	37
Commodity | Not Designated as Hedging Instrument | SWEPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Not Designated as Hedging Instrument | SWEPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	11	11
Commodity | Not Designated as Hedging Instrument | SWEPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	3	2
Commodity | Designated as Hedging Instrument | Current Risk Management Assets
Derivative [Line Items]
Total Assets	64	56
Commodity | Designated as Hedging Instrument | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	51	63
Commodity | Designated as Hedging Instrument | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	20	16
Commodity | Designated as Hedging Instrument | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	16	5
Commodity | Designated as Hedging Instrument | AEP TEXAS INC. | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | AEP TEXAS INC. | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | AEP TEXAS INC. | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | AEP TEXAS INC. | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | APCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | APCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | APCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | APCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | I&M | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | I&M | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | I&M | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | I&M | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | OPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | OPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | OPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | OPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | PSO | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | PSO | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | PSO | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | PSO | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | SWEPCo | Current Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | SWEPCo | Long-term Risk Management Assets
Derivative [Line Items]
Total Assets	0	0
Commodity | Designated as Hedging Instrument | SWEPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Commodity | Designated as Hedging Instrument | SWEPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	16	16
Interest Rate (USD) | Designated as Hedging Instrument | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	16	13
Interest Rate (USD) | Designated as Hedging Instrument | AEP TEXAS INC. | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | AEP TEXAS INC. | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | APCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | APCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | I&M | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | I&M | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | OPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | OPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | PSO | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | PSO | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | SWEPCo | Current Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	0	0
Interest Rate (USD) | Designated as Hedging Instrument | SWEPCo | Long-term Risk Management Liabilities
Derivative [Line Items]
Total Liabilities	$ 0	$ 0